Abstract: An electronic flow instrument and method which uses the instrument for monitoring and/or controlling the production or flow of a fluid. The instrument has a multiplexer linked by a USB connection to a microcontroller so that the multiplexer provides multiple USB connection ports for the microcontroller. A resident USB flash drive is installed in one of the USB connection ports for storing long term logging data related to the production or flow of the fluid. Secure access to the electronic flow instrument is provided by using a second USB flash drive containing a security file or password as a security key.